A multiplicity of seat belt structures exists in the prior art. Standards for loading have been established by among others the Federal Motor Vehicle Safety Standard, and specifically in 49 C.F.R. Chapter 5, Section 571.207, Standard No. 207, and Section 571.210, Standard No. 210 seat belt assembly anchorages. Within each of these aforementioned standards there is described a test procedure outlining the applicable forces which must be sustained and the center line or contact point of those forces as well as the duration of the application of such forces. In reviewing the prior art in seat related track structures, there appears to be a lack in the prior art wherein the upper and lower tracks when subjected to such loaded tests do not interact nor interengage, but have a general tendency to separate from one another. Such a separation under normal seat belt loading may very well have disastrous consequences to the operator of the vehicle. A significant number of track profiles have been tested and loaded to determine the deficiencies in the prior art in an attempt to access the cause of the separation of these well known track profiles.
Before a track assembly can be well received in the marketplace it must be well designed, easy to manufacture, with a high level of beam stiffness or a section modulus. It would also be very desirable for the track to promote interlocking between the upper and lower rails during the loading process. Another beneficial attribute of such a track would be that it would be light weight requiring less material while remaining superior in performance.
In conducting the standard tests described above, typically the upper rail is subjected to a peeling load through the seat belt anchor when in its various adjusted positions and the track must withstand the predetermined maximum load for a predetermined period of time. In relating this test to the prior art, referring now to the European Patent Application 98,740 of TI Cox Limited and published in 1984 a double J profile is illustrated and described. The upper track has a general double J, one of the J's being a mere image of the other, the upper track being inserted in a lower track having a general U-shape and having inwardly extending appendages which extend towards the larger upwardly extending portion of each of the J portions.
U.S. Pat. No. 4,564,236 issued on Jan. 14, 1986 in favour of Keiper Recaro GmbH & Co., also describes a double J track of alternative formation wherein the inwardly extending appendages of the generally U-shaped fixed track extend down toward the bottom of the double J portions at substantially 90.degree.. These tracks have been tested for their interlocking abilities and it has been determined that when subjected to a sufficient load, the upwardly extending shorter portions of each J tend to press against the bending portion of the adjacent surfaces of the bottom track and tend to open up the bottom track providing a minimum of interrelationship during the loading of the track. In conclusion, this profile does not tend to interlock when subjected to a sufficient load, but tends to separate. This track assembly therefore restrains occupants by the material strength of the flanges of both the upper and lower tracks. It is customary therefore to form these tracks from thicker gauge metal.
Another form of track profile available in the prior art is found in U.S. Pat. No. 3,926,397 wherein is described and illustrated a generally U-shaped stationary track having engaged therewith a generally C-shaped track as the moveable track. Again when subjected to a load the top track will tend to open up, thus resulting a separation of the track portions during extreme loading compensated again by the thickness of material. U.S. Pat. No. 4,487,459 describes a similar type device which will again tend to separate and open up with respect to one another during the loading.
U.S. Pat. No. 4,422,612 describes a moveable and fixed rail which is extruded from aluminum and which has a set of two tab portions on the moveable rail and a set of tab portions on the fixed rail. The bottom set interengage or lock with teeth during normal operation, but again when subjected to a load would only withstand the load according to the material strength of the tab portions 13 and 6. These portions will interengage during normal use, but do not tend to bind down upon each other when subjected to loads. In fact, the teeth may shear as seen in FIG. 3, and thus provide a considerable amount of play in the track during loading. There is no provision for the collapsing of one track around another and the interlocking aspects thereof.
Finally, U.S. Pat. No. 4,262,963 describes a guide rail assembly which is very complex and a good example of involved profiles found in the prior art. When subjected to loading, there is not found in the description of the invention in the U.S. Pat. No. 4,262,963 any aspect of collapsing or interlocking which would be highly desirable in performance of a structural track.
Nowhere within the prior art is there found a structural track assembly which when subjected to a peeling load from the seat belt anchor (attached to the moveable rail) will interlock with respect to one another because of the nature of the profile of the moveable track in relation to the fixed track, thus enhancing the performance of the track assembly. It is to this end which the instant invention addresses itself.
It is therefore an object of this invention to overcome the deficiencies in the prior art described above and provide a structural seat track which will interlock when subjected to separating loads.
It is a further object of this invention to provide a seat track structure which is easy to manufacture and economical.
It is a further object of this invention to provide a seat track which improves the safety performance of known prior art seat tracks.
Further and other objects of the invention will become apparent to a man skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.